CO2 hydrogenation to synthetic fuel via modified Fischer-Tropsch process using cobalt-based catalysts

Abstract: The effect of promoting Co/Al2O3 catalyst with potassium on CO2 hydrogenation to longerchain hydrocarbons was investigated. The catalysts used in this study were synthesized using an incipient wetness impregnation of the support with cobalt nitrate solutions. All catalysts were supported on γ-alumina and promoted with potassium (0 – 8 wt.%) and/or 0 – 3 wt.% of either copper, ruthenium or palladium. The synthesized catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), tempetature programmed reduction (TPR) and CO2 temperature programmed desorption (CO2–TPD) analyses. The catalysts were evaluated for CO2 hydrogenation using a fixed-bed tube reactor. The effect of reaction temperature (190 – 345 oC) during CO2 hydrogenation was evaluated at atmospheric pressure to determine the optimum reaction temperature that would favor the formation of longer chain hydrocarbons. Once the optimum temperature was selected, the effect of pressure (1 – 20 bar) was evaluated to determine the optimum operating pressure under the selected optimum temperature...D.Phil. (Chemical Engineering

CO2 hydrogenation to liquid hydrocarbons via modified Fi scher Tropsch over alumina supported cobalt catalyst s : effect of operating temperature, pressure and potassium loading

Abstract: The effect of promoting 15%Co/Al2O3 catalyst with potassium on CO2 hydrogenation to longer-chain hydrocarbons was investigated. The catalysts used in this study were synthesized using an incipient wetness impregnation of the support with nitrate solutions. All catalysts were supported on γ-alumina and promoted with potassium (0 – 8%). The synthesized catalysts were characterized by XRD, BET, XPS, TPR and CO2-TPD analyses. The catalysts were evaluated for CO2 hydrogenation using a fixed-bed tube reactor. The CO2 conversion was found to increase with both the reaction temperature and pressure. The TPR data revealed that potassium limited the reduction of the catalyst, decreased the selectivity to methane and increased the selectivity to C2+ hydrocarbons. The maximum C2+ yield of 10.2%, with CO2 conversion of 42.3%, was obtained when 6 wt.% of potassium was added to the catalyst. It is believed that during the CO2 hydrogenation process over the catalysts that were promoted with potassium, CO2 is first converted to CO via reverse–water–gas–shift reaction, followed by subsequent hydrogenation of CO to hydrocarbons

Fischer-Tropsch synthesis over unpromoted Co/ɣ-Al2O3 catalyst: effect of activation with CO compared to H2 on catalyst performance

Abstract : The effect of activating Co/Al2O3 catalyst by diluted CO or H2 on catalyst performance for Fischer-Tropsch reaction was investigated. The catalyst was prepared by incipient wetness impregnation of the support and characterized using BET N2 physisorption, SEM and XRD analyses. The reduction behavior of the catalyst in presence of CO and H2 individually was evaluated using TPR analyses. The data reveal that CO activates Co/Al2O3 catalyst at a lower temperature than H2 and produces a catalyst with higher rate for liquid product formation. It also leads to higher methane selectivity probably due to some cobalt carbide formation

Design and Development of Water-splitting Electrocatalysts Based on Conjugated Triazine Frameworks

Covalent triazine frameworks (CTFs) with rich nitrogen atoms and permanent porosity have been widely used in the field of opto/electronics as supports. In this study, two CTFs with different pore sizes (single pore and heteropore) were synthesized, after which Cu2+, Co2+, Ni2+, Pd2+, Pt2+, and the corresponding metal cluster were introduced into the CTFs as catalytic active sites through the confinement effect of the pores. Among a series of CTFs-based electrocatalysts, DCP-CTF-Pt2+ displays an outstanding electrocatalytic performance with an overpotential of 46 mV and a Tafel slope of 30.2 mV dec-1. Catalytic kinetics analysis indicates that electrocatalytic performance is closely relevant to hierarchical pore and metal size

Catalyst deactivation rate during hydrogenation of CO2 to longer chained hydrocarbons over 6 wt.% potassium-promoted Co/Al2O3 catalyst

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Fischer-Tropsch reaction over alumina-supported cobalt catalyst : activation using H2 and CO

Abstract: The catalytic activity for Fischer-Tropsch (FT) reaction over cobalt-based catalysts mainly depends on two parameters, namely the reducibility of cobalt precursors and cobalt dispersion. Therefore, a perfect catalyst would comprise of an optimal combination of these two parameters. Cobalt precursor’s reduction is usually performed in the presence of H2 and is usually limited by metal-support interactions which, in some cases, lead to the formation of metal-support compounds that are not reducible under a practical reduction temperature range. The water vapour that is formed during cobalt-based reduction by H2 has been reported to promote the formation of these metal-support compounds in some cases. An investigation on a reduction process that does not produce water would potentially offer opportunities for better cobalt-based catalyst reduction. Therefore, the aim of this project was to investigate the effect of activating Co/Al2O3 FT catalyst using H2 or CO on the catalyst structure and performance for FT reactions. The catalyst was prepared by impregnation of the support (Al2O3) with a cobalt nitrate (Co(NO3)2•6H2O) solution and calcined in air at 500°C for 10 hours to decompose and transform the cobalt nitrate to cobalt oxide. XRD analysis was performed to determine the structure of the catalyst prepared. BET analysis was performed to determine the surface area and porosity of the catalyst. Temperature programmed reduction (TPR) was performed on calcined Co/Al2O3 catalyst using a H2 and CO containing gas mixture respectively to study the reduction behaviour of the catalyst. The catalyst morphology was studied using scanning electron microscopy (SEM) analysis. The catalyst was tested for FT reaction in a fixed bed reactor and the outlet gas products were analysed using a Dani master gas chromatograph (GC) equipped with thermal conductivity detector (TCD) and flame ionisation detector (FID). It was found that CO activates the Co/Al2O3 catalyst at a lower temperature than H2 and is accompanied by carbon deposition on the catalyst surface. The main forms of cobalt species in catalyst samples reduced by CO or H2 at 300 oC were CoO. Co0 and CoO were the major cobalt phases for the catalyst samples respectively reduced by CO and H2 at 350 oC. The highest catalytic activity for FT reaction with the highest rate of C5+ hydrocarbons formation were measured on CO-activated catalyst samples. The deposited carbon on COreduced samples is believed to be a precursor for possible cobalt carbide formation during FT reaction that led to high methane selectivity.M.Tech. (Chemical Engineering

Effect of Support Particle Size in Fischer–Tropsch Synthesis: the Use of Natural Clinoptilolite as Support

In the past, Fischer–Tropsch (FT) coal/biomass-to-liquids projects have required a significant initial investment. The high price of the catalysts used is one area where costs could be reduced. This research explored the possibility of using clinoptilolite as a catalyst to reduce costs without sacrificing performance. The as-received clinoptilolite was ground and sieved to yield different size classes. For this study, three size classes were investigated as the support for an FT catalyst: −75 to +53 μm; −53 to +38 μm; less than 25 μm. Using a fixed bed reactor, 10% cobalt supported on these various supports was synthesized and evaluated. The maximum CO conversion obtained was 44.97% when using the −53 to +38 μm size class with the experiments carried out at 220 °C, 2 L(NTP)/(gcat h) and 10.85 bar(abs). A one-way analysis of variance was performed. Then a posthoc Bonferroni adjustment test was carried out to determine whether or not the utilization of different support size classes affected CO conversion. The results indicated a significant difference in CO conversion, with P(T ≤ t) two-tail values ranging from 6.08 × 10–5 to 2.37 × 1027. At 220 °C and 10.85 bar(abs), methane selectivity ranged between 14.95 and 16.97% for the support class sizes studied, while C2–C4 selectivity ranged between 14.55 and 19.01%, and C5+ selectivity ranged between 66.04 and 70.29%. The acquired product selectivity results using this cheaper support are comparable to those reported in the literature. These discoveries might have valuable implications for the design of a catalyst that can be used in the coal/biomass to liquid process